$userID = 123; // user ID of the user whose group we want to retrieve $user = CUser::GetByID($userID); if($userData = $user->Fetch()){ $userGroup = $userData['GROUP_ID']; echo "User group for user ID ".$userID." is ".$userGroup; }In this example, we first fetch the user information from the database using the GetByID function. We then retrieve the user group ID from the user data and output it to the screen. This code example uses the Bitrix framework library. Overall, GetUserGroup function in PHP is useful when you need to retrieve information about a user's membership in a particular group. This information can be used in a wide range of applications, from displaying customized content to restricting access to certain areas of a website based on user permissions.